Fluidized beds have been used for a number of different applications such as gas-liquid, gas-liquid-solid contactors and to carry out a variety of different processes including chemical reactions such as ion exchange.
Fluidized beds have found application in ion exchange processes. For example Chase, H. A., “Purification of Proteins by Adsorption Chromatography in Expended Beds”, TIBTECH 12, 296-303 (1994) describes a batch ion exchange process using a conventional fluidized bed for recovering proteins from whole fermentation broth with the presence of bacterial cells. It eliminates the difficult solids separation step and recovers the desired products directly from unclarified whole broth. This process is a batch process employing a conventional fluidized bed.
Burns, M. A. and D. J. Graves, “Continuous Affinity Chromatography Using a Magnetically Stabilized Fluidized Bed”, Biotechnology Progress 1, 95-103 (1995) suggested a two-column magnetically stabilized fluidized bed system for the continuous chromatography of biochemical products. The magnetically stabilized fluidized bed system is considered to be complicated and costly.
Gordon, N. F., H. Tsujimura and C. L. Cooney, “Optimization and Simulation of Continuous Affinity Recycle Extraction”, Bioseparation 1, 9-12 (1990) describes a process using mixed reactors as opposed to a fluidized bed and reported the continuous affinity recycle extraction of proteins using well-mixed reactors. This system, although simple and easy to control, has the disadvantage of a stirred tank system—the ion exchange efficiency is low and large processing volumes are essential for even a moderate throughput requirement.
Further, various forms of apparatus have been described for use in such chemical processes.
Porter and Robert, U.S. Pat. No. 3,879,287, “Continuous ion exchange process and apparatus” (1975) relates to an apparatus for continuous ion exchange. However, the process described is a semi-continuous process as the recommended eluting means is a batch wise conventional fixed bed ion exchange process.
Himsley and Alexander, U.S. Pat. No. 4,279,755: Continuous countercurrent ion exchange process (1993) teaches a continuous countercurrent ion exchange process for adsorbing ions of interest onto ion exchange particles from a feed liquor containing ions which when adsorbed on the particles cause the density of the particles to increase. The process comprises the steps of (1) flowing the feed liquor upwardly through a main bed of ion exchange resin particles contained in a main chamber of an absorption column and thereby maintaining the bed in fluidized state; (2) continuously collecting the denser loaded particles from the lower region of the absorption column; (3) passing an outflow of the feed liquor from the upper region of the main chamber upwardly into the lower region of the polishing chamber containing a secondary bed of fluidized ion exchange resin particles whereby residual ions of interest are polished from the liquor, and (4) producing a barren liquor flowing out of the upper region of the polishing chamber. While this process offers continuous flow of feed liquor to the system, the movement, stripping and regeneration of the loaded ion exchange particles device is done on an intermittent basis.
Bassi et al., U.S. Pat. No. 6,716,344 describes a liquid solid continuous fluidized bed (LSCFB) comprising a conventional fluidized bed for adsorption of ions and a riser co-current fluidized bed for desorption of ions and regeneration of ion exchange particles. Ion exchange particles circulate continuously between the fluidized beds. The LSCFB is useful for continuous recovery of ions of interest, however, the nature of the design results in low particle regeneration efficiency, it consumes unfeasibly large quantities of fluids, and in most applications, it results in significant dilution of process streams.